Process for concentrating formaldehyde solutions



Aug. 9, 1932. F. WALKER 1,871,019

PROCESS FOR CONCENTRATING FORMALDEHYDE SOLUTIONS Filed March 26. 1930 BIY ' ,3. WM ATTORNEY Psteated'Au 9, 1932 UNITED STATES A CORPORATION OF DELAWARE HASSLACEER cannon. COMM,

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This invention relates to concentration of m comprises vaporizing dilute formaldehyde solutions, condensing the major portion of condensed after entering the first condensing an zone are subjected to a minimum of washing or scrubbing by condensatereturning to the still and more especially by hot condensate. In this respect thepresent process is almost diametrically opposite to the usual fractional 2a distillation process carried out in theordinary fractionating column wherein the vaors are bubbled through or otherwise kept in intimate contact with the returning condensate.

Contrary to the views commonly held l[ helieve that formaldehyde and water, both 1n the vapor phase, exist as substantially separate entities. Furthermore, it is my opinion that formaldehyde vapor has a substantially "small solubility in cold water althoughv in contact with warm or hot water it readily forms soluble hydrates. In turn, if the warm formaldehyde solutions are cooled, complex formaldehyde-water polymers form. My .method of separation reverses the steps just delineated. Formaldehyde solutions are heated and depolymerization follows; the solutions are vaporized, water vapor with some formaldehyde is condensed out and hyde vapor is removed from contact, so far and as soon as possible, with all water which ,iis not in cooled liquid form toward which the formaldeh de behaves as it were as an inert, tt-substantia insoluble gas. I do not desire to The process according to this invention cooled as quickly as possible. The formaldei PATENT OFFICE rnnnn'mc "WALKER, or NEW nnron'ron, swarm: 1am, .miw vomr, assronon, an I I unsivn ASSIGNMENTS, we ran aonssmn a be bound bymy theoryilhowever, as the same may involve error. It as been given to picture as exactl as my present howledge al.- lowsthe fun amental principles to be followed in practising my invention. In the accompanying drawihg, Fig. l.-il-,

lustrates, diagrammatically, an apparatus suited for carryin out this process. 1 inv dicatesa still in w ich the dilute iormaldehyde solution'is vaporized. Mounted above the still is a still head com rising a vertical column 2 having a vap r inlet 3 adja cent the bottom, and communicatin the still a return line 4 to the still 1 1s provided at the bottom of the column for reflux return. The vertical column 2 is provided with a vapor outlet 5, adjacent its upper end which leads to a spiral condenser 6', within the water iiacket 7.

Central y located wikhinthe column 2 is an elongated water coo ed condenser 8, provided with water inlet 9, and a water outlet 10. This condenser 8 extends below the vapor inlet 3 and accordingly, the vapors from the still immediately contact withthis portion of condenser 8 as soon as they enter the still head. A considerable fportion of the water and a minor portion 0 formaldehyde in the vapors condense at this point and return at once tolthe still through the return line 4. The uncondensed vapors, which now contain .ahi her ercent of formaldehyde than the dish ate irect from the still, proceed up the column away from the major portion of the'condensate. As the vapors travel up the column 2, further condensation takes place to a small degree and hence the vapors come in contact with a. minimum' amount. of condensate in the still head.- Moreover, the condensate flowing down the condenser is cooled, thus minimizing reab so tion in the reflux.

still head of does not contain any pacmng, lass rings or the like, adapted to increase t e surface of with p the present invention condensed li uid presented to the vapors ascending in t e column and in this respect, also contrary'to some known ap aratns constructed for formaldehyde distillation, the present apparatus does not employ what 1a.;

enerally known as a fractionating column.

t has been found that the upright column of the still head in the present apparatus need be no more than 10 times the diameter of said column and would not be made as a practical proposition, more than times the diameter of the column, whereas the combined length of the fractionating column and still head heretofore used to a large extent in this art, is approximately 100 times as long as the diameter thereof.

I To illustrate results attainable by the proces of this invention, the following specific example is given:

Example I the run, 7 portions of concentrated formaldehyde solution were taken from the receptacle to obtain data showing the progress of the distillation at frequent intervals. The temperature of the vapor in the still was between approximately 9395 C.

Percent Weight Weight Per- .0! gg Changes of Reflux Portion of porcent CHaO CH 0 concenmm) tion omo in pori trateslnstfll moved By taking portions 1, 2, 3, 4, and '5, of the above .table and 150 gms. of portion 6, a 40% formaldehyde solution would be obtained containing 91.4%of the formaldehyde of the original still charge.

- Although the processof. my invention has been described with reference to only one forlin of apparatus, it is evident that a wide variation in the design'and materials composing the apparatus is possible without de art-' ing from the scope of my invention. I ave shown for example, a long and narrow stillhead whereas thesaid still-head can be narrow at the vapor outlet and wide at the distillate inlet and function satisfactorily. In the illustrative apparatus the condenser is below the vapor inlet, other forms of apparatus are suitable, however, as long as the formaldehyde vapor contacts withrelatively cool reflur: and to relatively small extent. Any material might be used in building the apparasider as within the scope of my invention any v and all reasonable equivalents of the same. Ordinary myinvention will be applied to solutions containing less than 40% formaldehyde since 40% formaldehyde is the common commercial article of the present day. It can however also be applied to solutions of other strengths.

I claim: 1. Process of concentrating solutions of formaldehyde in less volatile liquids comprising vaporizing the solution, fractionally condensing the major part of the vapors, re-

turning the condensate to the solution being vaporized without substantial washing or scrubbing contact with the vapors distilling from said solution, and passing the uncondensed vapors to a-condenser.

2. Process of-eoncentrating aqueous solutions of formaldehyde comprising vaporizing the solution, condensing a fraction of the vapors returning the condensate to the solution being vaporized without substantial washing or scrubbing contact with the vapors distilling from said solution, and passing the .uncondensed vapors to a condenser.

3. Process of concentrating aqueous formaldehyde solutions of less than 40% formaldehyde by weight comprising vaporizing the solution, condensing a fraction of the vapors thus produced, separating the remaining vapors from thecondensate as quickly as practicable and returning the condensate to' the still, and separately condensing said remaining vapors.

.4. Process of concentrating aqueous for-' maldehyde solutions of less than 40% for-' maldehyde by weight comprising vaporizing the solution, condensing a fraction of the vapors, returning the condensate to the solution being va rized 'without substantial washing or scru bing contact with the vapors distilling from said solution, and passing the uncondensed vapors to a condenser.

Si ed at Perth Amboy in the county of Mid esex and State of New J ersey'this 24th March, A. D. 1930.

day of FREDERIC WALKER. 

